The plasma processing equipment is widely used in the field of microelectronics technologies.
Reference could be made to FIG. 1 which is a structural schematic diagram of a usual plasma processing equipment.
Plasma processing equipment 1 usually comprises a housing 11, in which a reaction chamber 12 with a top electrode plate 13 and a bottom electrode plate 14 arranged face to face respectively on the top and the bottom of the reaction chamber 12 is formed. The top electrode plate 13 is separated from the housing 11 by an insulating member 15; and a workpiece to be processed can be held on the surface of the bottom electrode plate 14. Said workpiece should include wafer and other workpieces having the same processing principle as the wafer. The term “workpiece” used in the following will have the same meaning.
In the operation of the plasma processing equipment 1, a vacuum producing apparatus (not shown in the Figure) such as a dry pump produces and keeps a status approximate to vacuum. In such status, the process gas is delivered into the reaction chamber 12 by a gas distribution apparatus 16, and an appropriate RF power is applied across the top electrode plate 13 and the bottom electrode plate 14 to activate said process gas, so that a plasma environment is produced and kept on the surface of the workpiece. Due to the strong etching and deposition capabilities, the plasma can make physical and chemical reactions such as etching and deposition with the workpiece, such that the required etching pattern or deposition layer is obtained. The by-product of the physical and chemical reactions is pump out from the reaction chamber 12 by the vacuum producing apparatus.
As is known to all, the degree of uniformity of distribution of the process gas on the surface of the workpiece is of key importance to the quality of workpiece. With increase of the overall size of the workpiece such as a wafer, the area of the cross section of the reaction chamber 12 becomes larger and larger, and it is more and more difficult to achieve a uniform distribution of the process gas.
The degree of uniformity of distribution of the process gas relates to various factors, wherein, to a great extent, the structure of the gas distribution apparatus determines the uniformity of distribution of the process gas in the reaction chamber.
Reference could be made to FIG. 2 which is a structural schematic diagram of a usual gas distribution apparatus.
The usual gas distribution apparatus 2 comprises a support plate 21 with a substantially round shape, which is located at the central position of the top of the plasma processing equipment and is fixedly connected to a top electrode plate in a conventional manner, and an air inlet 211 is arranged in the center of the support plate 21.
A showerhead electrode 23 with a substantially round shape and coaxial with the support plate 21 is fixedly connected below the support plate 21, and the connecting portion between the support plate 21 and the showerhead electrode 23 is gas sealing (the term “gas sealing” used here and the term “gas sealing” used in the following means a consequence rather than a means; that's to say, no matter what a concrete technical means is used, a phenomenon of gas leakage should not appear in the connecting portion between the support plate 21 and the showerhead electrode 23), a gas distribution chamber is formed between the support plate 21 and the showerhead electrode 23. The air inlet 211 communicates with the gas distribution chamber.
Multiple layers of flow choking plates 22 are arranged in the gas distribution chamber in a conventional manner, and a suitable distance is kept between respective layer of the flow choking plate 22, as well as between the flow choking plate 22 and the support plate 21, and between the flow choking plate 22 and the showerhead electrode 23, thus, the gas distribution chamber is divided into several small chambers from top to bottom. The flow choking plate 22 comprises a plurality of gas passages 211 each of which penetrates through the flow choking plate 22 in its axial direction, so that one small chamber can communicate with another.
Because the gas passages 211 in respective layers of the flow choking plate 22 are staggered, the process gas is forced to be subjected to a certain lateral displacement, and thus the radial uniformity is improved; as the number of the layers of the flow choking plate 22 increases, times that the process gas is subjected to a lateral displacement increases, thus the radial uniformity of the process gas obtained on the upper surface 232 of the showerhead electrode 23 is accordingly improved.
A plurality of gas holes 231, which are used to make the lowest small chamber of the gas distribution chamber communicate with the reaction chamber below the showerhead electrode 23, are uniformly distributed in the showerhead electrode 23. The comparatively uniform process gas on the upper surface 232 of the showerhead electrode 23 can flow into the reaction chamber of the plasma processing equipment through the gas holes 231.
However, as mentioned above, the gas distribution apparatus forces the process gas to be subjected to a lateral displacement by means of a hindrance function of the flow choking plate 22, so that the radial uniformity of the process gas is improved; thus, in order to obtain a improved lateral uniformity, many layers of flow choking plates 22 are required. As a result, the gas distribution apparatus mentioned above is structurally complex and huge in volume, and the manufacturing cost is also high; while a reduction of the number of the flow choking plates 22 will reduce the uniformity of process gas distribution.
Therefore, the gas distribution apparatus in the art either is too complex and has high manufacturing cost, or can't obtain high uniformity of process gas distribution. Skilled in the art has an urgent technical problem to solve, that is, how to simplify the structure of the gas distribution apparatus while making sure that the uniformity of process gas distribution is not reduced.